Momentum Definition and 1000 Threads

Taking the Earth orbiting the sun as an example, when I consider the angular momentum of the Earth about the sun, should the spin angular momentum be counted? I'm confused that if it's counted, the spin angular momentum, Lcm=Icm×ωspin, is different from other angular momentum regarding the...

Hello, I'm trying to calculate the measurement of the orbital angular momentum of the state l=1 and m = -1. The operator for the angular momentum squared is ## L^2 = -\hbar (\frac{1}{sin\theta}(\frac{\partial}{\partial \theta}(sin\theta\frac{\partial}{\partial \theta}))...

Homework Statement (Problems/diagrams referenced are attached as images.) Homework Equations Net torque about an origin = time derivative of the angular momentum vector about the same origin. The Attempt at a Solution I've solved these problems before, but I'm now looking back at them and...

Homework Statement The payload of a spaceship accounts for 20% of its total mass. The ship is traveling in a straight line at 2100km/hr relative to some inertial observer O. When the time is right, the spaceship ejects the payload, which is moving away from the ship at 500km/hr immediately...

Homework Statement A point particle travels in a straight line at constant speed, and the closest distance it comes to the origin of coordinates is a distance l. With respect to this origin, does the particle have nonzero angular momentum? As the particle moves along its straight-line path...

Hello. My name is John. I have an undergraduate degree in Mathematics. I am now classified as a senior citizen. I have always been interested in science. I've been following the progress of NASA's Parker Solar Probe and in the latest blog, Geoff Brown of Johns Hopkins University Applied Physics...

Good afternoon I just have this little doubt: imagine the osculating orbit of Mars changing slowly in its elements along the centuries. The semi major axis changes, the period, etc. Is the specific angular momentum allways equal in all the osculating orbits Mars has in those centuries? Or does...

Homework Statement Two pucks are lying on ice where they can slide and rotate with almost no friction. A string is tied to both pucks but it is tied to the middle of the first puck and wrapped around the second puck. You pull on both strings with the same force, F. The first puck moves without...

Homework Statement A bomb initially at rest is exploded into three pieces on a smooth, horizontal surface. Two pieces fly off at a 60° angle to each other, a 2.0 kg piece at 20 m/s and a 3.0 kg piece at 12 m/s. The third piece flies off at 30 m/s with an unknown direction. Determine the...

Homework Statement [/B] The total mass of a space shuttle and its launch vehicle is M=2000t. a) What must be the minimum size of the thrust force, to make the rocket move? b) The actual thrust of the rocket is F=30MN. What is its acceleration in the beginning? c) Assume that a mass of a...

Homework Statement A pumpkin of mass 3.30kg at rest on a smooth frictionless plane, explodes into 3 pieces in the horizontal plane. A .50kg piece flies to the North at 3.2m/s. A 1.4kg piece flies off (SW) at 4.1m/s. What is the speed, direction and mass of the third piece? Homework Equations...

1. The problem statement. A tennis ball of mass m moving horizontally with speed u strikes a vertical tennis racket. The ball bounces back with horizontal speed v. Homework Equations p = mv The Attempt at a Solution My answer was m(v-u), meaning the final momentum (mv) subtracted from the...

I have a 5.0 m tractrix and am trying to work out angular momentum and total angular momentum for two hitchpoint speeds 60 & 70 km/h. My result shows a higher total angular momentum for the lower speed. This is not what I expected. Here are my equations Positions: Derivatives Angular velocity...

Homework Statement I understand that if the change in impulse is 0.25, that because disc B is originally stationary the momentum disc B will have is equal to the impulse. My question is how do we do this in terms of change in momentum? Homework Equations ΔP = Pf - Pi P = mv The Attempt at a...

Hi. I'm reading an introductory text that somehow seems to confuse if ##E^2-(cp)^2=const## means that the left side is invariant (under Lorentz transformations) or conserved (doesn't change in time). As far as I understand it, they only prove Lorentz invariance. Are they both true? If so...

Hi. I've read that there's no Newtonian analogue of the energy-momentum relation $$E^2-(pc)^2=(mc^2)^2\enspace .$$ Why doesn't $$E=\frac{p^2}{2m}$$ qualify as such? There's no rest energy in Newtonian physics anyway.

I'm trying to deduce the angular momentum ( for a rigid body ) on my own, and here is the problem I face. By introducing the angular momentum of a tiny piece in rigid body (" i ") as : Li = ri × pi Li = ri × mi vi --------------------------------- [ Line 1 ] Li = ri × mi ri ωi To find the...

Homework Statement if you wanted to build a spring launched cannon that will shoot you over a building that is 35 m high and 30 m wide, and the cannon is being shot at 60 degrees. If the cannon can be no more than 2 m long, what spring constant do you need in the spring to make this work? here...

Homework Statement An atomic nucleous of mass m traveling with speed v collides elastically with a target particle of mass 3.0m (initially at rest) and is scattered at 45o (a). What are the final speeds of the two particles? Advice: eliminate the target particle's recoil angle by manipulating...

I've started on "Noether's Theorem" by Neuenschwander. This is page 35 of the 2011 edition. We have the Lagrangian for a central force: ##L = \frac12 m(\dot{r}^2 + r^2 \dot{\theta}^2 + r \dot{\phi}^2 \sin^2 \theta) - U(r)## Which gives the canonical momenta: ##p_{\theta} = mr^2...

Generalized momentum is covariant while velocity is contravariant in coordinate transformation on configuration space, thus they are defined in the tangent bundle and cotangent bundle respectively. Question: Is that means the momentum is a linear functional of velocity? If so, the way to...

Hello, I encountered the following statement in my lecture notes and there is a couple of things I don't understand:"Let's consider two particles with spins ##s_1 = \frac{1}{2}## and ## s_2 = 1## with a spherically symmetric interaction potential. Assume these two particles are in a two...

Homework Statement Not a HW problem, but a "me re-thinking things" problem. Please tell me where my thinking is flawed: You have an ice skater with no net external torques acting on him/her. (We are analyzing the time after they have to get an external torque on them by pushing off of the...

Homework Statement Fission, the process that supplies energy in nuclear power plants, occurs when a heavy nucleus is split into two medium-sized nuclei. One such reaction occurs when a neutron colliding with a 235U (uranium) nucleus splits that nucleus into a 141Ba (barium) nucleus and a 92Kr...

Hey! I am new on the forum and I joined because I really enjoy physics but I have a horrible teacher. I was wondering if anyone could help me on a question how do I find the velocity at the end of the zipline? how do I find the momentum of the object going down the zipline after it is...

Homework Statement A uniform thin rod AB is equipped at both ends with the hooks as shown in the figure and is supported by a frictionless horizontal table. Initially the rod is hooked at A to a fixed pin C about which it rotates with a constant angular velocity w1 . Suddenly end B of the rod...

A 50.0-kg male dancer leaps 0.32 m high. (a) With what momentum does he reach the ground? I know that to find momentum the equation is P = mv, but I only have the mass and distance. I have tried finding the time (D = 1/2at^2) and later used that time to find the velocity (v = d/t). I later used...

A question came up about deducing the number of possible energy states within a certain momentum ##p## using momentum space. To make my question easier to understand, I deliberately chose ##p## and not a particular increment ##dp## and I assume a 2 dimensional momentum space with coordinates...

The released products of a transmutation reaction (I say transmutation when 2 particles reacts to generate more than one) follows the conservation of kinetic energy law. Also particles moving in opposite direction can have equal speed one with respect the other than rather if one of them is...

Homework Statement A particle (5 kg) moves with constant velocity 2 m/s along the straight line 2y=3x+4, the angular momentum of the particle about origin is? Homework Equations L=r x p The Attempt at a Solution For a 2d problem we take the component of velocity perpendicular to the point...

I have a disc that is rotating due to air being blown at its outer radius. The incoming relative velocity of the air is high, therefore the effect of friction supersedes the effect of conservation of angular momentum. The tangential portion of this velocity decreases due to the friction as it...

Homework Statement Consider a classic wedge and block system, (block on top of wedge(inclination theta)). there is friction between the block and wedge (not enough to prevent block from sliding). All other surfaces are smooth. For the motion that follows after releasing the block from rest, is...

Homework Statement [/B] A skier (mass M = 100 kg) going down a slope with inclination θ = 30°, sliding in a fluid-like snow (viscosity μ = 100 mPa*s) of thickness h = 0.01 m, using a pair of skis, each one with a surface area of As = 0.15 m2, reaches terminal velocity vt after some distance...

Homework Statement A disk of radius ##r## and mass ##m## rolls down an inclined plan. It reaches the end of the plane with velocity ##v_{f}## and collides with a vertical rod of length ##L## and mass ##M## sticking with it. See figure. What is the angular momentum magnitude and direction...

Homework Statement Homework Equations ##\hat{P}= -ih d/dx## The Attempt at a Solution To actually obtain ##\psi_{p_0}## I guess one can apply the momentum operator on the spatial wavefunction. If we consider a free particle (V=0) we can easily get obtain ##\psi = e^{\pm i kx}##, where ##k=...

So Pearson is telling me that, basically, the ratio of internal to external forces and the briefness of the time interval is what determines whether the external forces on a system whose momentum we're studying will affect whether we can obtain a decent approximation of the momenta of the...

Homework Statement A ball of mass ##m## is attached to a massless string of length ##L##. The ball is released from rest as shown in the figure and as it reaches the bottom of the circle, the string wraps around a nail which is a distance ##d## below the center of the circle. What is the...

I wish to draw the proton momentum spectrum by transforming the energy spectrum of recoil protons. I have calculated the energy spectrum using Nachtmann's spectrum: wp=g1[T]+a*g2[T] Where: g1[T]=(1 - x2/σ[T])2 * Sqrt[1 - σ[T]] * (4*(1 + x2/σ[T]) - (4/3*(σ[T] - x2)/σ[T])*(1 - σ[T])); g2[T]=(1 -...

Homework Statement A spigot pours beans onto a scale platform. At a time t = 0.0 sec, the spigot is opened and beans begins to pour out (with initial velocity 0) at a rate of 1.00 kg/sec onto the platform from a height of 10.0 m above. (a) At t = 10.0 sec, what is the weight of beans on the...

We are all familiar with Heisenbergs uncertainty principle. When we determine the position of a particle or wave, the uncertainty of momentum reach infinity. So let's say I have a machine that measures the position very very precisely. Then the uncertainty of this non-moving particles momentum...

Although I thought that I understand special relativity enough, I cannot now clearly answer on the following question: What is the most direct derivation, why momentum in special relativity is ##p=\gamma m v##, where ##v## is velocity of the rocket? Let us assume that Lorentz equations are...

Homework Statement The Fourier transfrom of the wave function is given by $$\Phi(p) = \frac{N}{(1+\frac{a_0^2p^2}{\hbar^2})^2}$$ where ##p:=|\vec{p}|## in 3 dimensions. Find N, choosing N to be a positive real number. Homework Equations $$\int d^3\vec{p}|\Phi(p)|^2=1$$ , over all p in the 3...

Hello again Physics Forums! I have a question about fluid dynamics. Perhaps someone here can help me out. I am trying to understand how a plume of water moving at some speed carries momentum within a body of water. For instance the ‘exhaust’ from a submarine propeller. I am having a hard time...

1. The problem statement I want to write the angular momentum operator ##L## for a 2-dimensional harmonic oscillator, in terms of its ladder operators, ##a_x##, ##a_y##, ##a_x^\dagger## & ##a_y^\dagger##, and then prove that this commutes with its Hamiltonian. The Attempt at a Solution I get...

25.0-kg dog is trapped on a rock in the middle of a narrow river. A 66.0-kg rescuer has assembled a swing with negligible mass that she will use to swing down and catch the trapped dog at the bottom of her swing, and then continue swinging to the other side of the river. The ledge that the...

Homework Statement A 2.4 kg particle-like object moves in a plane with velocity components vx = 25 m/s and vy = 80 m/s as it passes through the point with (x, y)coordinates of (3.0, −4.0) m. (Express your answers in vector form.) (a) What is its angular momentum relative to the origin at this...

Homework Statement A mass m_1, initially moving at a speed v_0, collides with and sticks to a spring attached to a second, initially stationary mass m_2. The two masses continue to move to the right on a frictionless surface as the length of the spring oscillates. At the instant that the...

Homework Statement A space person is motionless a distance of 500m away from the safety of the spacecraft . The person has exactly 11.32min of air left and the person's mass is 103.2kg, including equipment. The person throws a phaser at a velocity of 50.2km/h away from the spacecraft in order...

Homework Statement A rod of length D sits at rest on a friction less table. A ball of mass M strikes the end of the rod with a speed V and rebounds with a speed 3v/4 causing the rod to rotate counterclockwise around a fixed axis at one end. The rotational inertia of the rod is I Homework...

Homework Statement A Texas cockroach of mass 0.17 kg runs counterclockwise around the rim of a lazy Susan (a circular disk mounted on a vertical axle) that has radius 15 cm,rotational inertia 4.9 ✕ 10^−3 kg · m2, and frictionless bearings. The cockroach's speed (relative to the ground) is 2.0...